Investments in Nuclear Decommissioning Trusts and Other Special Use Funds (Details) - ARIZONA PUBLIC SERVICE COMPANY - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Nuclear decommissioning trust fund assets
Fair Value	$ 1,087,235	$ 901,358
Total Unrealized Gains	230,781	260,160
Total Unrealized Losses	(7,237)	(2,996)
Amortized cost	635,000	467,000
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	6,680	21,830	$ 11,213
Realized losses	(13,552)	(13,155)	(10,106)
Proceeds from the sale of securities	653,033	546,339	633,410
Equity securities
Nuclear decommissioning trust fund assets
Fair Value	447,138	425,044
Total Unrealized Gains	222,147	248,623
Total Unrealized Losses	(459)	0
Fixed income securities
Nuclear decommissioning trust fund assets
Fair Value	637,356	475,716
Total Unrealized Gains	8,634	11,537
Total Unrealized Losses	(6,778)	(2,996)
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	88,022
1 year - 5 years	217,352
5 years - 10 years	130,890
Greater than 10 years	201,092
Total	637,356
Other Receivables from Broker-Dealers and Clearing
Nuclear decommissioning trust fund assets
Fair Value	2,741	598
Total Unrealized Gains	0	0
Total Unrealized Losses	0	0
Nuclear Decommissioning Trusts
Nuclear decommissioning trust fund assets
Fair Value	851,134	871,000
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	6,679	21,813	11,213
Realized losses	(13,552)	(13,146)	(10,106)
Proceeds from the sale of securities	554,385	542,246	633,410
Nuclear Decommissioning Trusts | Equity securities
Nuclear decommissioning trust fund assets
Fair Value	402,008	424,614
Nuclear Decommissioning Trusts | Fixed income securities
Nuclear decommissioning trust fund assets
Fair Value	446,978	446,277
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	26,819
1 year - 5 years	97,566
5 years - 10 years	128,379
Greater than 10 years	194,214
Total	446,978
Nuclear Decommissioning Trusts | Other Receivables from Broker-Dealers and Clearing
Nuclear decommissioning trust fund assets
Fair Value	2,148	109
Coal Reclamation Escrow Accounts | Fixed income securities
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	21,237
1 year - 5 years	15,658
5 years - 10 years	2,511
Greater than 10 years	6,878
Total	46,284
Active Union Medical Trust | Fixed income securities
Fair value of fixed income securities, summarized by contractual maturities
Less than one year	39,966
1 year - 5 years	104,128
5 years - 10 years	0
Greater than 10 years	0
Total	144,094
Other Special Use Funds
Nuclear decommissioning trust fund assets
Fair Value	236,101	30,358
Realized gains and losses and proceeds from the sale of securities by the nuclear decommissioning trust funds
Realized gains	1	17	0
Realized losses	0	(9)	0
Proceeds from the sale of securities	98,648	4,093	$ 0
Other Special Use Funds | Equity securities
Nuclear decommissioning trust fund assets
Fair Value	45,130	430
Other Special Use Funds | Fixed income securities
Nuclear decommissioning trust fund assets
Fair Value	190,378	29,439
Other Special Use Funds | Other Receivables from Broker-Dealers and Clearing
Nuclear decommissioning trust fund assets
Fair Value	$ 593	$ 489